Near‐Earth asteroid (101955) Bennu is an active asteroid experiencing mass loss in the form of ejection events emitting up to hundreds of millimeter‐ to centimeter‐scale particles. The close proximity of the Origins, Spectral Interpretations, Resource Identification, and Security–Regolith Explorer spacecraft enabled monitoring of particles for a 10‐month period encompassing Bennu's perihelion and aphelion. We found 18 multiparticle ejection events, with masses ranging from near zero to hundreds of grams (or thousands with uncertainties) and translational kinetic energies ranging from near zero to tens of millijoules (or hundreds with uncertainties). We estimate that Bennu ejects ~10⁴ g per orbit. The largest event took place on 6 January 2019 and consisted of ~200 particles. The observed mass and translational kinetic energy of the event were between 459 and 528 g and 62 and 77 mJ, respectively. Hundreds of particles not associated with the multiparticle ejections were also observed. Photometry of the best‐observed particles, measured at phase angles between ~70° and 120°, was used to derive a linear phase coefficient of 0.013 ± 0.005 magnitudes per degree of phase angle. Ground‐based data back to 1999 show no evidence of past activity for Bennu; however, the currently observed activity is orders of magnitude lower than observed at other active asteroids and too low be observed remotely. There appears to be a gentle decrease in activity with distance from the Sun, suggestive of ejection processes such as meteoroid impacts and thermal fracturing, although observational bias may be a factor.

中文翻译：

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从活性小行星喷出的粒子的光度法（101955）Bennu

近地小行星（101955）Bennu是一颗活动的小行星，它以喷射事件的形式经历质量损失，发射出的微粒高达数百毫米到厘米。起源，光谱解释，资源识别和安全性—Regolith Explorer航天器非常接近，因此可以在10个月的时间内对包括Bennu的近日点和顶针的粒子进行监测。我们发现了18个多粒子喷射事件，其质量范围从接近零到几百克（或成千上万个不确定性），平移动能范围从接近零到几十毫焦耳（或成百上千个不确定性）。我们估计Bennu弹出〜10 ⁴ 每轨道克。最大的事件发生在2019年1月6日，由约200个粒子组成。该事件的观测质量和平移动能分别在459和528 g之间以及62和77 mJ之间。还观察到数百个与多粒子喷射无关的粒子。在〜70°和120°之间的相角处测得的最佳观察粒子的光度法用于得出每相角度为0.013±0.005量级的线性相系数。追溯到1999年的地面数据没有显示Bennu过去的活动的证据。但是，目前观测到的活动比其他活动小行星观测到的活动低几个数量级，而远距离观测到的活动太低。距太阳的距离似乎在逐渐减少，